I'm glad there are so many expert chemists here that can tell me how toxic a given chemical is. One such expert has claimed that EDTA is very toxic, but it is injected as a counter to heavy metal poisoning. It and the metal are safely eliminated from the body. Also, Hypo is used as an antidote for Cyanide poisoning. And yet, dumping it down the drain is forbidden? Well, hair dye is really akin to a Kodachrome developer. There is a CD4 analog and a Magenta coupler analog in there to dye hair for a red-brown look. Drain cleaners are strong chemicals. Some are pure Sulfuric Acid and some are strong alkali or contain Phosphates.
Dumping down a drain is at the "whim" of the locale in which you live. My usage at its peak was so small, I doubt that anyone could even detect any effluent, but the rules here are not really that strong. The Kodak effluent was another matter. The effluent contained significant Silver ion and Cadmium ion, with the latter being far worse than the former. Kodak eliminated most all of that in the late '60s.
PE
Glad too - and thanks for clarifying the issue about concrete toxic characteristics of lab chems.
Perhaps some different definitions of "toxic" are the reason of missunderstandings.
1) toxic to the enviroment - in most cases - with exeption of "clean" h2o.
2) toxic to water- and other organism ( du ducks for example)
3) toxic to humans (often in the long term perspective)
4 ) lethal dosis (on rats or mice )
.......All is in relative concern.
But the M O S T interest to people in darkroom is : " Is this chemical good for my health "
So my point is - If you are working with the general care (you have to find out for "EACH" chemical) - It is most relative how often you will use such "special" chems in darkroom.
Are you a darkroom enthusiast ?
(4 times a week for the whole night)
Or is your darkroom allways closed with the exeption on every 2. Friday evening. And are you using problematic chems just 2 times a year?
The difference to proffessionals is therefore enormously. Remember some (relative) problematic chems -
(you mentioned some) wich were relative often in use wirthin the past.
And if you then "add" the dose of some years or some decades to proffessional lab persons you soon will see the motivation of "modern" restrictions.
(environmentaly danger is not so much the focus because of much less of that chems today in relation to polution in the past)
with regards
PS : The lab I worked as a trainee years ago didn't care of any regulation. (They did not handle any toxic materials. ...

They solve their problem one time a week at midtnight - the smal river they used beside their plant was quite ok for that reason. NO DUCKS NO FISHES
That was the procedure within the 30th/during-behind the war, within the 50th and 60th why not proceed during the late 80th.
Until the day some local residents informed the police (they can't sleep at midtnight some days per month due to a breath-taking stench everywhere)
And because of some older woman who wondered about - they can't remember any duck swimming on the pretty lake beside their upper class villas since soo many years.
So officials closed the plant - they
had not the resources to pay the money fine at last (120 employers).
